1. Field of the Invention
The present invention relates to a surgical instrument, commonly called a "trocar instrument" or "device," or simply a "trocar," that is used to pierce the wall of an anatomical cavity thereby forming a passageway providing communication with the inside of the cavity. Other medical instruments such as endoscopes, arthoscopes, and operating instruments can thereafter be inserted through the passageway to perform various medical procedures within the anatomical cavity.
Surgical techniques using trocar devices to pierce anatomical cavity walls have recently gained great favor in the expanding field known as "least invasive surgery." Such techniques have been widely employed, for example, in gall bladder surgery and their use for other types of operations is actively being explored and implemented. These methods are desirable because the passageway formed by the trocar is small and neat. Therefore, the major trauma associated with large surgical incisions, used to perform certain operations in the past, can be avoided.
The present invention provides an improved safety trocar instrument that is well suited to least invasive surgical techniques. By its design the safety trocar instrument of the present invention not only avoids the trauma that results when large incisions are made in an anatomical cavity wall, but also reduces the chance that unintended and unwanted trauma will result particularly after the instrument penetrates the wall.
2. Description of the Prior Art
In its elemental form, a trocar is a device comprising an elongated shaft of, for example, surgical steel having a sharpened blade or point. Typically, least invasive surgery using such a device is performed first by inserting a fine surgical or "Veress" needle through the cavity wall and thereafter injecting a fluid into the cavity to insufflate it and separate the cavity wall, including muscle and the peritoneum in the case of the abdomen, from other internal organs like the heart, stomach, and major blood vessels. The sharpened point of the trocar is then placed against the cavity wall and urged to pierce it by manually applying pressure to the proximal end of the shaft. An outer sleeve or "cannula" may be slid over the shaft through the wound created by the sharp point. The sleeve permits the shaft to be withdrawn from the cavity wall and maintains the passageway into the cavity. Observation and surgical instruments can then be introduced into the cavity through the sleeve.
Ordinarily, the cavity wall exerts relatively large resistance to penetration by the trocar point. However, once the wall is pierced that resistance is relieved, often suddenly, so that the sharp trocar point may suddenly be urged deeply into the cavity. Therefore, the risk exists that the sharp trocar point will injure vital organs in the cavity. Accordingly, attempts have been made to reduce that risk.
For example, U.S. Pat. No. 4,654,030 (Moll, et al.) discloses a safety trocar device that includes a trocar subassembly and a trocar tube subassembly that interfit with, but are separable from, one another. The trocar subassembly includes a grip, a trocar or "obturator" having a sharpened piercing tip or point, an axially reciprocally mounted tubular obturator sleeve or shield, and a compressed coil spring for urging the shield forwardly essentially to surround and shield the piercing tip of the obturator. The trocar tube subassembly includes a main body and an elongated trocar tube. The trocar device is used by inserting the obturator and shield of the trocar subassembly into the trocar tube of the trocar tube subassembly. The shield and piercing tip are together urged to extend through the lumen of the trocar tube. Ordinarily, the shield is locked in this extended position. However, when unlocked the shield may withdraw into the trocar tube against the urging of the compressed spring in the trocar subassembly.
In order to pierce an anatomical cavity wall, the shield is first unlocked. Its exposed distal end is placed against the anatomical cavity wall by applying pressure to the assembly. The resistance exerted by the wall causes the shield to retract axially into the trocar tube thereby to expose the piercing tip of the obturator. Thus the tip may puncture the cavity wall. Once the tip and shield have penetrated the wall and have entered the anatomical cavity, the resistance exerted by the wall on the distal end of the shield is relieved permitting it to be urged by the compressed spring back to its extended position surrounding the piercing tip. Accordingly, once the resistance of tee cavity wall on the distal end of the shield is released, the chances of injury to internal organ structures are reduced because the sharp portions of the piercing tip are again covered by the shield.
U.S. Pat. No. 4,535,773 (Yoon) also relates to a safety puncturing instrument or trocar for puncturing an anatomical cavity wall and discloses several embodiments of that instrument. A number of the embodiments are conceptually similar to that disclosed in the Moll Patent and include an outer sleeve or obturator tube with an elongated section defining an interior lumen opening at a distal end and extending through to a proximal end. A thin-walled inner sleeve or shield is mounted coaxially within the outer sleeve and is urged by a compression spring to protrude from the lumen at the distal end of the outer sleeve. A trocar or obturator has a sharp blade at its distal end that can be inserted into the inner sleeve so that, when seated, the blade projects beyond the distal end of the outer sleeve but is encircled and shielded by the distal end of the inner sleeve.
These embodiments of the safety puncturing instrument disclosed in the Yoon Patent are used by inserting the trocar into the inner and outer sleeves and placing the distal end of the inner sleeve against the wall of an anatomical cavity. Force is then applied to the proximal end of the trocar so that the outer sleeve and trocar blade are forced toward the cavity wall. The distal end of the inner sleeve is urged to retract within the distal end of the outer sleeve by resistance exerted by the cavity wall, thereby compressing the spring and permitting the trocar blade to be exposed to pierce the wall.
When the outer sleeve enters the wound created by the trocar blade, the inner sleeve is held completely within the outer sleeve by the resistance of the cavity wall to passage of the distal ends of the outer and inner sleeves. As force continues to be applied to the proximal end of the trocar, the sharp point passes through the cavity wall and enters into the cavity. The force also causes the outer sleeve to follow through the wound. As the distal ends of the outer and inner sleeves clear the inner surface of the inside of the cavity wall, the resistance of the wall is relieved thereby releasing the inner sleeve, which is then returned to its extended position by the spring to shield the trocar blade.
Safety trocars like those described above and disclosed in the Moll and Yoon Patents have certain inherent drawbacks. First, because the piercing tip of the trocar blade is generally shielded when the instrument is placed against the anatomical cavity wall, it is necessarily shielded from the surgeon's view. Therefore, he or she cannot be certain that the tip will puncture the wall at the precise location desired. Moreover, after the piercing tip has penetrated the cavity wall, it must protrude a further substantial distance into the anatomical cavity before the inner sleeve or shield is released again to cover the tip. Thus, a substantial period remains during which the tip is exposed and may injure internal organ structures. In the Yoon devices, since the inner sleeve or shield and outer sleeve may remain in the cavity after the trocar is removed, they often project a substantial distance into the cavity. Thus the available space in the cavity within which the surgeon can work is reduced.
The Yoon Patent also discloses another embodiment, shown in its FIGS. 34 and 35, that includes structure for causing the sharp trocar point to retract inwardly into the outer sleeve. More particularly, this structure includes a puncturing implement or trocar having a shaft with a large diameter section at its distal end terminating in a sharp blade and a point that bears one or more electrical pressure sensors or transducer elements. An intermediate section of the trocar has a reduced diameter and is able to slide within a hollow proximal tubular section. A tension spring is coupled between the proximal end of the intermediate shaft section and a plug threaded into the proximal end of the tubular section. A detent mechanism holding a small detent is mounted in the intermediate shaft section. The detent is urged radially outwardly by a compression spring. When the intermediate shaft section is fully extended outwardly from the tubular section, the detent is coaxially aligned with and protrudes radially into a small hole in the wall of that tubular section. Thus, the shaft of the trocar is locked in the fully extended position against the urging of the coil spring, which is then held in tension.
The whole assembly is carried in an outer sleeve. When the trocar is locked in the extended position, its blade extends beyond the distal end of that sleeve.
Electrical leads pass through the interior of the shaft of the trocar and connect the blade sensors to electrical contacts within the detent, and in turn to an electrical socket.
To use the instrument, the trocar is first locked in its outwardly extended position with the detent radially engaged in the detent hole. The trocar-tubular section assembly is then fitted with a handle and the distal end of the trocar is inserted into the outer sleeve. When that assembly is fully inserted into that sleeve, the detent is coaxially aligned with a radial solenoid socket adjacent the electrical socket. An electrical plug assembly includes an electrical jack that connects the leads from the blade sensors through the socket to an alarm network.
The trocar assembly may then be used by pressing the blade against the anatomical cavity wall such that counterforce exerted by that wall on the blade sensors is converted to a sequential set of ready signals that trigger the alarm network. As the blade passes through the wall into the cavity interior, the counterforce is relieved from the blade sensors sequentially to produce a set of electrical signals through the alarm network. When the penetration is complete, the electrical signals from the sensors cause the alarm network to actuate the solenoid, thereby depressing the detent to permit the tension spring to retract the blade into the sleeve.
An alternative detent structure is illustrated in FIG. 36 of the Yoon Patent.
While in many respects this latter embodiment of the Yoon invention is an improvement over the other safety trocar designs described in the Yoon and Moll Patents, it nevertheless suffers from certain serious disadvantages. First, it depends on electrical pressure sensors or transducer elements connected to an alarm network to sense release of the counterforce exerted by the anatomical cavity wall and thereby to trigger retraction of the trocar point. Therefore, proper operation of the device may be destroyed by an electrical power failure or interruption that, even if brief, can result in serious injury to the patient. Further, the device is not self-contained but must instead be connected to the external alarm network. That alarm network may be cumbersome and the electrical leads connecting the trocar device to the alarm network may well interfere with the surgeon's work.
Therefore, still additional improvement to safety trocar instrument design would be greatly beneficial to the surgical community.